Dissertations / Theses on the topic 'Phénomènes quantiques'
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Le, Bihan Soazig. "Comprendre les phénomènes quantiques." Thesis, Nancy 2, 2008. http://www.theses.fr/2008NAN21008/document.
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Rech, Jérôme. "Phénomènes quantiques macroscopiques dans les systèmes d'électrons fortement corrélés." Phd thesis, Université Paris Sud - Paris XI, 2006. http://tel.archives-ouvertes.fr/tel-00197118.
Restrepo, Cadavid Juliana. "Décohérence et thermalisation des systèmes quantiques." Paris 6, 2011. http://www.theses.fr/2011PA066394.
Carosella, Francesca. "Étude théorique des phénomènes de transport électronique dans les puits quantiques AlGaN/GaN." Lille 1, 2005. http://www.theses.fr/2005LIL10125.
Nous avons ensuite abordé l'étude des mécanismes de diffusion intrinsèques, en établissant pour ces systèmes bidimensionnels le potentiel diffuseur associé aux pseudo particules hybrides, résultant de l'interaction entre les phonons optiques et les plasmons. Fort de cette base, qui a permis pour la première fois le calcul de la mobilité théorique maximum, nous avons pu enfin aborder l'étude des centres diffuseurs extrinsèques les plus déterminants Nous avons démontré qu'ils étaient liés à la présence de dislocations ainsi qu'à la qualité des interfaces présentant des rugosités (ou des fluctuations) liées aussi bien à leur structure géométrique qu'à la répartition hétérogène des charges d'interface La comparaison de nos résultats théoriques avec différents résultats expérimentaux a permis de démontrer que les dislocations introduisent des niveaux extrinsèques légers situés à environ 110 meV sous la bande de conduction de GaN et que leur potentiel détermine en grande partie la mobilité des échantillons contenant de faibles valeurs de densité de porteurs, alors que les mécanismes de rugosité, caractérisés par le biais d'un paramètre de corrélation, sont responsables de la chute des valeurs de mobilité dans le domaine des hautes densités de porteurs libres. Ces résultats devraient permettre d'affiner les méthodes de croissance cristalline selon le domaine de densité de porteurs qui sera choisi pour la réalisation des composants
Viale, Yannick. "Etude de boîtes quantiques de CdZnTe : processus de relaxation d'énergie et de phase." Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/VIALE_Yannick_2004.pdf.
We present a study of the electron-hole pair energy and phase relaxation processes in a CdTe/ZnTe heterostructure, in which quantum dots are embedded. CdZnTe quantums wells with a high Zinc concentration, separated by ZnTe barriers, contain islands with a high cadmium concentration. In photoluminescence excitation spectroscopy experiments, we evidence two types of electron hole pair relaxation processes. After being excited in the CdZnTe quantum well, the pairs relax their energy by emitting a cascade of longitudinal optical phonons until they are trapped in the quantum dots. Before their radiative recombination follows an intra-dot relaxation, which is attributed to a lattice polarization mechanism of the quantum dots. It is related to the coupling between the electronic and the vibrationals states. Both relaxation mechanisms are reinforced by the strong polar character of the chemical bond in II-VI compounds. Time resolved measurements of transmission variations in a pump-probe configuration allowed us to investigate the population dynamics of the electron-hole pairs during the relaxation process. We observe a relaxation time of about 2 ps for the longitudinal phonon emission cascade in the quantum well before a saturation of the quantum dot transition. We also measured an intra-box relaxation time of 25 ps. The comparison of various cascades allows us to estimate the emission time of a longitudinal optical phonon in the quantum well to be about 100 fs. In four waves mixing experiments, we observe oscillations that we attribute to quantum beats between excitonic and biexcitonic transitions. The dephasing times that we measure as function of the density of photons shows that excitons are strongly localized in the quantum dots. The excitonic dephasing time is much shorter than the radiative lifetime and is thus controlled by the intra-dot relaxation time
Giamarchi, Thierry. "Localisation et interactions dans les fluides quantiques unidimensionnels." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37605448p.
Alrifai, Rim. "Fonctions optiques robustes dans des structures de guides d'onde : liens avec des phénomènes quantiques." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0087.
Wave propagation in coupled optical waveguides and population dynamics in quantum systems composed of coupled discrete levels share a common mathematical formalism related to the underlying Schrödinger equation. In the context of this thesis the key role is played by the relation between robust adiabatically evolving quantum systems and corresponding adiabatically evolving waveguide systems. In the optics case the robustness reflects in a strongly increased tolerance with respect to changes in wavelength (achromaticity), temperature, or unwanted variations in the waveguide parameters.Earlier works in our laboratory in the context of the above analogy were related to waveguides allowing propagation of the fundamental mode only and did not consider the possible propagation of both orthogonal polarization modes. In the present thesis we fill this gap by discussing ways for achieving broadband polarization separation as well as broadband mode conversions. The investigated systems are composed of three coupled waveguides with a spatial adiabatic evolution. In addition, we consider a third system where a dissipation in one of three waveguides allows to achieve ultra-broadband power splitting despite for the absence of any adiabatic evolution of the waveguide parameters.Integrated polarization beam splitters (PBS) play a significant role in many integrated photonic devices where the polarization state of light requires manipulation and important efforts are under way to make such a functionality as broadband as possible. Our proposal in this context involves a three-waveguides configuration with anisotropic refractive index either in the core or in the cladding and is inspired by the quantum STIRAP process (STImulated Raman Adiabatic Passage). Our analysis shows that an anisotropy ratio of 5 (ratio between the refractive index contrasts for the TM and TE waves) is sufficient for separating efficiently the two polarizations over a spectral range of ≈ 350 nm around the 1550 nm central wavelength. The bandwidth of such PBS increases by increasing the anisotropy factor and the central wavelength can be adjusted by modifying the waveguides.One of the ways presently envisaged for increasing the nearly saturated capacity of optical telecommunication systems relies on space division multiplexing, where signals are transmitted on different spatial modes of a multimode optical fiber. This kind of approach requires elements capable of demultiplexing the modes by separating and converting them. Our proof of concept in this context is based again on an adiabatic three-waveguide systems and permits conversion between a higher order mode and the fundamental mode (or vice-versa) over a wide spectral range. The underlying waveguide design is again analogous to the above quantum STIRAP process or in alternative to Adiabatic Elimination (AE) in which case the central waveguide is strongly detuned from the two others.As mentioned above, the third system studied in this thesis does not rely on adiabatically evolving waveguides but is related to the behavior of non-Hermitian quantum systems, specifically to quantum population transfer through a decaying intermediate state. Our approach is based on three parallel waveguides of which the central one is highly dissipating. It leads to ultra-broad band power division that has to be paid by a 50% overall loss if equal power is wished in the two output ports. Here the absence of the slow adiabatic variation allows for more compact systems, especially if the central waveguide is of the plasmonic type.The three systems that are discussed in this thesis show the great potential of quantum-inspired approaches for robust photonics, where tolerant, versatile and broadband functionalities are required. While devices of this kind may be used principally in classical integrated photonics, their use for single photon management in quantum optics is also an attractive perspective
Querlioz, Damien. "Phénomènes quantiques et décohérence dans les nano-dispositifs semiconducteurs : étude par une approche Wigner Monte Carlo." Paris 11, 2008. http://www.theses.fr/2008PA112218.
This work studies the quantum phenomena that appear in nanometer-scaled electron devices. To this aim, Monte Carlo type simulations based on the Wigner-Boltzmann equations are performed. After a presentation of general theory, this equation which allows including collision effects in a quantum transport simulation is proved. The new Wigner Monte Carlo approach to solving it is introduced, and is employed to simulate resonant tunneling diodes (RTD). The results are consistent with Green's functions based calculations and simple experiments. The theory of decoherence is then applied to interpret the results and understand the emergence of semi-classical behavior in nanodevices. Phonon-induced decoherence is compared to the quantum Brownian motion model. The transition between resonant and sequential transport through a quasi-bound state is analyzed. In a RTD, the transition from a quantum active region to semi-classical access regions is observed. Quantum phenomena in the shor test MOSFETs demonstrated in research labs are then studied. A hybrid regime is evidenced, where both quantum transport and collisions play a significant role. Degeneracy effects and decoherence experienced by electrons in MOSFETs are studied. Comparisons with experimental results are then performed. Finally, two studies concerning nanostructures considered for electron devices of the future (carbon nanotubes and graphene nanoribbons) are proposed
Lassoued, Saïda. "Modélisation de transistors a homo et hétéro-jonctions, compatibles avec une filière submicronique : influence de phénomènes quantiques." Lyon, INSA, 1998. http://www.theses.fr/1998ISAL0089.
The aim of this work is the study of a submicronic bi polar transistor, compatible with a silicon technology (BICMOS), developed by CNET lndustry (Meylan-France). First of all, we discuss with the doping level profiles. We develop a (co)diffusion modeling into the polysilicon and the monocrystalline silicon underneath. Then, we present static electrical characteristics such Gummel's ones, and dynamic measurements such as capacitances. We consider the effects of process on device parameters such as current gain and cut-off frequency. These characterizations point out the technological drawbacks concerning the device behavior. The core of the subject lies in developing a bidimensional device simulator dealing with the so-called drift-diffusion model. Moreover, we have to model the electrical transport through a very thin oxide (15 A) located between polysilicon and monosilicon, which increases the gain current by decreasing the hale current. Then we add the resolution of the Schroedinger equation to make the simulations fully numerical. The method used for this former one is a transfer matrix algorithm. Finally, we study a hetero junction transistor structure: a bipolar transistor with a SiGe-doped base. This structure gives high cut-off frequency specified for RF applications
Décanini, Yves. "Phénomènes de résonance et renormalisation en espace-temps courbe." Habilitation à diriger des recherches, Université Pascal Paoli, 2008. http://tel.archives-ouvertes.fr/tel-00609537.
Grange, Thomas. "Relaxation et décohérence des polarons dans les boîtes quantiques de semi-conducteurs." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00333256.
Nous prenons tout d'abord en compte le couplage fort entre excitons et phonons optiques afin de calculer l'absorption interbande sous champ magnétique.
Nous calculons ensuite le temps de vie des états polarons, dont l'instabilité est due à leur composante phonon. Nous démontrons la nécessité de prendre en compte de manière détaillée les différents processus anharmoniques, dont l'efficacité dépend fortement de l'énergie du polaron. Ces calculs permettent d'expliquer les variations non monotones du temps de vie mesuré des polarons avec leur énergie.
Nous étudions ensuite la dynamique de relaxation dans les boîtes doublement chargées, où l'interaction spin-orbite, associée aux couplages électron-phonon, entraîne des processus de retournement du spin entre états singulets et triplets.
Finalement, nous étudions la cohérence optique de la transition intrabande fondamentale, dont l'élargissement avec la température est dû aux transitions réelles et virtuelles vers le deuxième état excité.
Giraud, Romain. "Effets quantiques mésoscopiques d'ions de terres rares faiblement couplés." Phd thesis, Université Joseph Fourier (Grenoble), 2002. http://tel.archives-ouvertes.fr/tel-00007452.
Lemaitre, Aristide. "Étude en magnéto-absorption de puits quantiques semimagnétiques CdMnTe / CdMgTe en présence d'un gaz d'électrons bidimensionnel - Phénomènes de ségrégation aux interfaces CdTe / CdMnTe." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1999. http://tel.archives-ouvertes.fr/tel-00645513.
Lemaître, Aristide. "Etude en magnéto-absorption de puits quantiques semimagnétiques CdMnTe/CdMgTe en présence d'un gaz d'électrons bidimensionnel : phénomènes de ségrégation aux interfaces CdTe/CdMnTe." Paris 6, 1999. https://tel.archives-ouvertes.fr/tel-00645513.
Sleiman, Ammar. "Simulation Monte-Carlo du transport électronique et des phénomènes de diffusion dans les hétérostructures III-V : application aux structures MODFET et DMT." Lille 1, 1996. http://www.theses.fr/1996LIL10157.
Collura, Mario. "Aspects hors de l'équilibre de systèmes quantiques unidimensionnels fortement corrélés." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0009/document.
In this thesis we have addressed some open questions on the out-of-equilibrium dynamics of closed one-dimensional quantum systems. In recent years, advances in experimental techniques have revitalized the theoretical research in condensed matter physics and quantum optics. We have treated three different subjects using both numerical and analytical techniques. As far as the numerical techniques are concerned, we have used essentially exact diagonalization methods, the adaptive time-dependent density-matrix renormalization-group algorithm (t-DMRG) and the Lanczos algorithm. At first, we studied the adiabatic quantum dynamics of a quantum system close to a critical point. We have demonstrated that the presence of a confining potential strongly affects the scaling properties of the dynamical observables near the quantum critical point. The mean excitation density and the energy excess, after the crossing of the critical point, follow an algebraic law as a function of the sweeping rate with an exponent that depends on the space-time properties of the potential. After that, we have studied the behavior of ultra-cold bosons in a tilted optical lattice. Starting with the Bose-Hubbard Hamiltonian, in the limit of Hard-Core bosons, we have developed a hydrodynamic theory that exactly reproduces the temporal evolution of some of the observables of the system. In particular, it was observed that part of the boson density remains trapped, and oscillates with a frequency that depends on the slope of the potential, whereas the remaining packet part is expelled out of the ramp. We have also analyzed the dynamics of the Bose-Hubbard model using the tDMRG algorithm and the Lanczos algorithm. In this way we have highlighted the role of the non-integrability of the model on its dynamical behavior. Finally, we have addressed the issue of thermalization in an extended quantum system. Starting from quite general considerations, we have introduced the notion of out-of-equilibrium temperature profile in a chain of Hard-Core bosons. We have analyzed the dynamics of the temperature profile and especially its scaling properties
Chiorescu, Irinel. "Effets quantiques magnétiques dans deux cas limites : molécules à haut spin et à bas spin." Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10198.
Rahimpour, Soleimani Hamid. "Spin relaxation in bulk CuCl and CdTe quantum wells." Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/RAHIMPOUR_SOLEIMANI_Hamid_2005.pdf.
We have studied the spin relaxation dynamics using nondegenerate pomp-probe measurements. This is possible if transitions from degenerate states to other states are mutually allowed and forbidden for circularly polarized light with different helicities. We have applied this technique to two types of semiconductors: bulk CuCl and CdTe/CdMnTe quantum wells. In CuCl, the polariton dispersion curve is scanned by looking at different excitation and detection wavelengths. We have performed these studies at low temperatures on monocrystalline samples on a subpicosecond time scale. We have evaluated how the optical properties close to the exciton resonance develop in time from induced absorption to gain, depending on the wavelength and the intensity of excitation. We have shown that the spin-flip time and the relaxation dynamics of exciton polaritons can be determined in the “spin-flip region” situated just below the polariton bottleneck where the studied polaritons are quite slowly propagating. Using this technique, we present the first measurements of spin relaxation times in CuCl. Below the spin-flip region, however, the spin memory of the polaritons is rapidly destroyed due to surface effects. Within the bottleneck region, the spin-flip time shortens significantly through exciton-exciton scattering processes which become important because of the high density of states and the exciton like character of the polaritons. In additions, we have presented a theoretical interpretation of spin relaxation in CuCl based on the invariant expansion method of an effective Hamiltonian. We consider two possibilities for exciton-spin relaxation: first due to scattering processes, in which the direction of Q is changed and second due to the exchange interaction between electrons and holes in conjunction with the center-of-mass motion of the excitons. In CdTe/CdMnTe quantum wells, the principle of the experiment relies on two optical transitions that share a common energy level. We demonstrate experimentally that in our undoped piezoelectric quantum well, the heavy-holes relax their spin (h =40 ps) more slowly than the electrons (e =8ps). We have explained our results in terms of phase space filling of the electron and hole bands, from which the excitons are made up
Bahr, Stefan. "Dynamique Quantique des Nanoaimants Moléculaires." Phd thesis, Grenoble 1, 2008. http://www.theses.fr/2008GRE10144.
The thesis deals with the quantum dynamics of the molecular magnets Fe8 and Mn6. In our experiments we use micro Hall sensors to study the spin dynamics via magnetization measurements. These sensors can operate in large area in temperature and magnetic field and they permit time resolved magnetization measurements with a temporal resolution better than a microsecond. The first part presents time resolved magnetization measurements on the single molecule magnet Fe8. We show several independent experiments which evidence different couplings of the spins and which allow to observe the quantum dynamics of the molecular spins. The study of the magnetization dynamics gives us a direct access to spin relaxation processes, in particular these experiments allow us to explore the interaction between spins and phonons. In this context we developed a « pump-probe » technique that uses two microwave pulses that are shifted in time to study the very fast spin dynamics. The second part concerns magnetization measurements on the single molecule magnet Mn6 using Hall magnetometry. A multitude of measurements with different temperatures and magnetic fields allow us to characterize the magnetic properties of the molecule. Finally, we present some numerical simulations, based on a dimeric model of the molecule (in the presence of symmetric and antisymmetric exchange interactions), that allow us to explain theoretically the observed tunnel transitions
Bahr, Stefan. "Dynamique Quantique des Nanoaimants Moléculaires." Phd thesis, Université Joseph Fourier (Grenoble), 2008. http://tel.archives-ouvertes.fr/tel-00338458.
La première partie présente des mesures d'aimantation résolues en temps de l'aimant moléculaire Fe8. Nous présentons plusieurs expériences indépendantes, qui mettent en évidence les différents couplages entre les spins et qui permettent d'observer la dynamique quantique des spins moléculaires. Les études de la dynamique de l'aimantation nous donne un accès direct au processus de relaxation de spin, en particulier ces études nous permettent d'étudier l'interaction entre spins et phonons. Dans ce contexte nous avons développé une technique « pompe-sonde » avec deux impulsions de micro-ondes décalées en temps pour étudier la dynamique très rapide des spins.
La deuxième partie concerne les mesures d'aimantation de l'aimant moléculaire Mn6 par magnétométrie Hall. De nombreuses mesures dans différents régimes en température et en champ magnétique nous permettent de caractériser les propriétés magnétiques de la molécule. Finalement, des simulations numériques qui s'appuient sur un modèle dimérique de la molécule (en présence des termes d'interaction par échange symétriques et antisymétriques) nous permettent d'expliquer théoriquement les transitions par effet tunnel.
Asghari, Zahra Sadat. "Highf requency optoelectronic devices in the mid infrared wavelength region." Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCC111.
Mid infrared (MIR) covers the region of the electromagnetic spectrum between optics and THz ranges. This frequency range is of great interest for applications in spectroscopy and free space optical communications. The progress on unipolar devices based on intersubband transitions, has introduced in the MIR a new family of semiconductor lasers and detectors. These optoelectronic devices are indeed based on optical transitions between electronic states in the conduction band of a complex sequence of quantum wells. Their characteristic lifetime is of the order of picoseconds and therefore intersubband devices have a great potential for wideband ultrafast applications.The aim of this work is the design of a system for high data bit rate free space optical communication in the mid infrared spectral region, with all the components operating at room temperature. To this end, we investigate the high frequency performances of quantum cascade detectors (QCD) and lasers (QCL).Firstly, we carefully explore the electrical and optical characteristics of QCD at 4.9 μm operating at room temperature. A detailed study of the band structure and charge distribution at different operating temperature and under different applied bias is reported. We demonstrate a background limited infrared photodetector (BLIP) temperature of 135 K and a detectivity at this temperature of 2 × 1011 Jones, which is at the state of the art. We then focus on QCD response to high frequency modulation. We engineered and realized an electronic system compatible with high frequency operation. We report an optical response up to 5.4 GHz with a 50 × 50 (μm)2 square mesa using a gold air-bridge technology. Thanks to rectification measurements, we show that the band-pass is limited by the specific detector bandstructure. For the high frequency modulation of QCLs, we develop a plug and play system with an optimization on the injection contact that allows the demonstration of a cut off frequency of 10 GHz, limited by the photodetector. Finally, we present a proof of principle demonstration of a free space optical communication experiment using a QCL and a quantum well infrared photodetector (QWIP) at 4 Gb/s. We use a Binary Phase-Shift Keying (BPSK) modulation technique and we obtain a bit error rate of 10(−5)
Vermeulen, Pierre. "Microscopie à illumination structurée et optique adaptative pour l'imagerie de fluorescence 3D dynamique." Phd thesis, Université Paris-Diderot - Paris VII, 2012. http://pastel.archives-ouvertes.fr/pastel-00777094.
Ferrini, Giulia. "Phénomènes de cohérence quantique macroscopique dans les jonctions Josephson bosoniques." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00680099.
Giraud, Alexandre. "Phénomènes hors équilibres de l'Univers inflationnaire en théorie quantique des champs." Phd thesis, Université Paris-Diderot - Paris VII, 2010. http://tel.archives-ouvertes.fr/tel-00640210.
Giraud, Alexandre. "Phénomènes hors équilibre dans l'univers inflationnaire en théorie quantique des champs." Paris 7, 2010. http://www.theses.fr/2010PA077031.
In this thesis I study the reheating era of the inflationarry Universe. This makes the link between the inflation of the Universe and the hot Big-Bang model. During it, the inflaton decays into matter which thermalises by its self interaction giving a statistical description to the Universe content. This work is realised in the quantum filed theory setup using out-of-equilibrium methods such as the 2-Particle-Irreducible effective action which allows to deal with the usual difficulties of out-of-equilibrium quantum field theory. First I study the case where matter is represented by scalar fields then by fermionic degrees of freedom, where classical approximation does not exist. I expand the effective action to the Next-to-Leading Order in an inverse number of matter fields expansion which allows to explore theories where the matter is strongly coupled to itself. In a second part I study the decoherence of primordial density fluctuations. The Inflaton can be seen as a quantum coherent condensate and its decay as a decoherence. This decoherence and this loss of purity is strongly related to the loss of information an observer has on the System if he's retrained to the Gaussian correlation functions subspace. This work shows that, even in the unusual case where the System is not coupled to an external thermal and/or incoherent environment, this one loose its initial coherence and purity to product degrees of freedom or entropy
Galli, Carminati Giuliana. "Etude des phénomènes groupaux en tant qu’amplification de l’inconscient selon un modèle quantique." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAS034/document.
Group phenomena have been used since antiquity in therapeutic, social, economic and political domains. According to Bion, the interactions between group members generate a “group unconscious” and its behaviour is governed and oriented by Bion's “basic assumptions.” The present work has been conducted during group analysis training at the Basque Foundation for the Investigation of Mental Health (OMIE) at Bilbao, consisting of eleven sessions. The participants are presented with an “absurd questionnaire” proposing 50 pairs of images, in each of which one image has to be chosen. The results are used to search through an unconscious amplification for evidence in favour of the influence of group dynamics on individual choices of the images proposed in the questionnaire. Our analysis finds some significant evidence for an effect of group dynamics both on the initial choice of the pictures and on the evolution of the number of changes (swaps) of picture choices across the eleven sessions. We find also some relations between the orientation of the answers in the groups as results of Multiple Variable Analysis and calculation of the distribution of Bernoulli's Entropy. We interpret these correlations as group effects in the light of Bion's view of group dynamics, which postulates an immediate onset of a group unconscious and its evolution during the group activity.Keywords: Group Dynamics, Unconscious Amplification, Quantic Model, Entropy
Delga, Alexandre. "Du phénomène quantique au dispositif macroscopique, transport électronique dans les détecteurs inter-sousbandes." Phd thesis, Université Paris-Diderot - Paris VII, 2012. http://tel.archives-ouvertes.fr/tel-00769454.
Delga, Alexandre. "Du phénomène quantique au dispositif macroscopique : transport electronique dans les détecteurs inter-sousbandes." Paris 7, 2012. http://www.theses.fr/2012PA077220.
The development of high performance infrared (3-20μm) detectors is driven by technological applications such as thermography and spectroscopy for gas sensing. Among them, Quantum Cascade Detectors are photovoltaic unipolar devices where the transduction happens in nanometric quantum wells and on picosecond timescales. This Phd thesis deals with the modelling of electronic transport in these structures. The aim is to organize the continuum of time and length scales that span from the quantum phenomenon to the macroscopic de vice. In a first part, we underline the main limitations of semi-classical models to understand the quantity related to the signal (current, responsivity): they neglect the characteristic time of coherent phenomena. A hybridization of these models with a density matrix formalism is proposed and discussed. In a second part, we showed that noise can and must be understood on the same timescale as the current. A rigorous treatment of micro-macro articulation reveals that shot and Johnson noises, far from being independent as usually considered, are indeed the short time and long time limit visions of thé scattering of quantized charges. At last, the main potentialities of the QCD are discussed
Dupic, Thomas. "Application des théories conformes étendues à des problèmes de physique statistique." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS260.
The study of critical phenomena in two-dimensional statistical physics is mainly performed with the help of conformal field theory and integrable models. The relationship between these two formalisms is an active field of research, particularly in the framework of the so-called non-rational theories. This thesis is focused on certain critical systems described by an extended conformal theory : a theory that presents additional symmetries. The first problem studied is the fully packed loop model (FPL). Loop models are non-local statistical models based on the description of assembly of polymers. In particular, they represent the interfaces formed by spin models. The FPL model is integrable and its spectrum reflects an underlying symmetry Uq(sl(3)). The link between this model and the W3 symmetry, a conformal symmetry extended by a three-dimensional field, is studied in detail, numerically (by exact diagonalization) and analytically. The relationship with loop models leads to the study of the non-scalar operator content of the W3 theory. The second problem concerns the calculation of entanglement in unidimensional quantum systems. In this context, the preferred object of study is the entropy of entanglement between a subsystem and its complement. For the fundamental state of a spin chain, the behaviour of this entropy as a function of the size of the subsystem is a clear marker of the criticality of the chain. In this manuscript, a new way of calculating these entropies in critical models is presented. It is based on conformal theories extended by a symmetry called orbifold. This method is particularly applicable to entropies of excited states or disjointed subsystems
Shevtsov, Oleksii. "Contribution à la théorie du transport quantique : isolants topologiques à base de graphène et phénomènes à fréquence finie." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00770160.
Aubrun, Guillaume. "Convexité en grande dimension, matrices aléatoires et théorie quantique de l' information." Paris 6, 2005. http://www.theses.fr/2005PA066374.
Teran, Garcinuno Francisco José. "Phénomènes dépendants du spin dans des structures à un puits quantique CdMnTe à modulation de dopage de type-n." Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10210.
Oullemine, Saïd. "Phénomènes d'interférences inter et intramoléculaires dans 130Te2 : application de la superfluorescence à la spectroscopie moléculaire." Lyon 1, 1997. http://www.theses.fr/1997LYO10202.
Javaux, Clémentine. "Etude de la réduction du phénomène de clignotement dans les nanocristaux semi-conducteurs de CdSe/CdS à coque épaisse." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://pastel.archives-ouvertes.fr/pastel-00799228.
Vaneph, Cyril. "Observation du phénomène de blocage anormal de photon dans le domaine micro-onde." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066509/document.
Photon blockade is observed when a two level system is strongly coupled to a cavity thus limiting the occupation number of the cavity mode to zero or one photon. This phenomenon is analogous to the Coulomb blockade effect in mesoscopic physics and has been observed in optics by coupling a single atom or a quantum dot to a cavity. The efficiency of the blockade, as measured by the second order auto-correlation function g2(0) increases with the non-linearity of the system in comparison to the cavity width. In this thesis, we present a theoretical and experimental study of a new blockade mechanism, called "anomalous photon blockade effect", in the microwave domain. This effect appears in photonics systems consisting of two coupled modes, where at least one of the mode is non-linear. In contrast to the standard blockade effect, perfect blockade (g2(0)=0) can be achieved with an arbitrary weak non-linearity strength. In the first part, we present a theoretical study of the anomalous blockade, and we use, in particular, a description in terms of gaussian states. To experimentally observe this effect, we have micro-fabricated two coupled superconductive resonators, where one of the resonator is frequency tunable and non-linear thanks to a SQUID. In the second part, we present the fabrication process and the characterization of our sample. Finally, we present the different techniques that we use to measure the auto-correlation function g2(τ). This measurement allowed us to demonstrate the anomalous blockade effect and to study its various properties as a function of the experimental parameters
Amezian, Koutaïba. "Interprétation théorique des phénomènes de capture électronique dans la collision O6+ + He à l'aide des méthodes AB-initio de la physique quantique." Lyon 1, 1990. http://www.theses.fr/1990LYO10003.
Hakim, Vincent. "La morphologie des amas et la mécanique quantique dans un environnement dissipatif : deux illustrations des méthodes de la physique des phénomèmes critiques." Paris 11, 1985. http://www.theses.fr/1985PA112082.
We use several methods developed in the field of critical phenomena in order to study other problems. We obtain the number of directed 2D-animals growing from an arbitrary root and we compute two related exponents, ν and θ, by taking some inspiration from the solutions of exactly solved models of statistical Mechanics. Then, we define and solve two models of irreversible growth (DLA and the Eden model) on the Bethe lattice. After that, we study quantum Mechanics in a dissipative environment, à la Caldeira-Leggett. We begin by the completely soluble motion of a free particle coupled to a thermal bath. Then, we study, with renormalization group methods, a transition occurring for the two-level system, at a critical value of the friction coefficient. We also relate this model to other well-known hamiltonians of solid state Physics, by using the relations between fermions and bosons in one dimension. Finally, we study the damped motion of a particle in a periodic potential and find a similar transition between diffusive
Dura, Julien. "Etude et modélisation des phénomènes physiques émergents pour la simulation de dispositifs électroniques à base de nanofils de silicium." Phd thesis, Aix-Marseille Université, 2012. http://tel.archives-ouvertes.fr/tel-00764112.
Golfin, Guilhem. "L’objectivité et le phénomène : une étude philosophique et historique du concept de causalité à la lumière de la physique relativiste et quantique." Paris, EHESS, 2014. http://www.theses.fr/2014EHES0155.
The causality became a central subject during the controversies that arose in the first three decades of the XXth century with the invention of new physical theories, the Theory of relativity and the Quantum Mechanics. This was the case because these new theories questioned the classical causality's form, and even the relevancy of causality in itself for a physical theory, when the traditional idea was that the intelligibility of nature requires absolutely such a relation. Physicists indeed thought that classical causality clarified a matter which was remained confuse within the philosophical doctrines. Hence, the radical changes brought up by the new physical theories lead to analyse scientific intelligibility, and in the same rime the nature and the signification of causality as it is understood by the physicists. The study of some of the great physicists' works, shows that physical causality is an ideal relation, the function of which is to founder the objectivity of the scientific discourse. By the way, it is impossible to consider it as a property of the world, but it must be taken for a hermeneutic category. It works inside a discourse which tries to give a form to phenomena, and which finds its meaning by denying ail nature's proper order
Sadri, Saïd. "Simulation du phénomène de transport perpendiculaire en régime statique dans les hétérostructures à puits quantique par le formalisme des fonctions de Green." Lille 1, 1996. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1996/50376-1996-9.pdf.
Raffaelli, Bernard. "Analyse semi-classique des phénomènes de résonance et d'absorption par des trous noirs." Phd thesis, Université Pascal Paoli, 2011. http://tel.archives-ouvertes.fr/tel-00653074.
Wald, Sascha Sebastian. "Thermalisation and Relaxation of Quantum Systems." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0129/document.
This study deals with the dynamic properties of open quantum systems far from equilibrium in d dimensions. The focus is on a special, exactly solvable model, the spherical model (SM), which is technically simple. The analysis is of interest, since the critical behaviour in and far from equilibrium not of mean-field type. We begin with a résumé of the statistical mechanics of phase transitions and treat especially the quantum version of the SM. The quantum dynamics (QD) of the model cannot be described by phenomenological Langevin equation and must be formulated with Lindblad equations.First we examine the dynamic phase diagram of a single spherical quantum spin and interpret the solution as a mean-field approximation of the N-body problem. Hereby, we find a quantum mechanical ‘freezing by heating’ effect. After that, we extend the formalism to the N-body problem, determining first the form of the Lindblad equation from consistency conditions. The SM then allows the reduction to a single integro-differential equation whose asymptotic solution shows, that the effective QD in the semi-classical limit is fully classical. For a deep quench in the ordered phase, we show that the QD strongly and non-trivially depends on d and derive the dynamic scaling behaviour and its corrections. The mathematical tools for this analysis are new results on the asymptotic behaviour of certain confluent hypergeometric functions in two variables
Estienne, Benoit. "Etude des systèmes critiques bidimensionnels possédant des symétries discrètes : les théories conformes parafermioniques, et leurs applications." Paris 6, 2009. https://tel.archives-ouvertes.fr/tel-00421566.
Iftikhar, Zubair Qurshi. "Quantification de la charge et criticalité quantique Kondo dans des circuits mésoscopiques avec peu de canaux." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS423/document.
This thesis explores several fundamental topics in mesoscopic circuitry that incorporates few electronic conduction channels. The first experiments address the quantized character (the discreteness) of charge in circuits. We demonstrate the charge quantization criterion, observe the predicted charge quantization scaling and demonstrate a crossover toward a universal behavior as temperature is increased. The second set of experiments addresses the unconventional quantum critical physics that arises in the multichannel Kondo model. By implementing a Kondo impurity with a pseudo-spin of ½ constituted by two degenerate charge states of a circuit, we explore the two- and three-channel Kondo physics. At the symmetric quantum critical point, we observe the predicted universal Kondo fixed points, scaling exponents and validate the full numerical renormalization group scaling curves. Away from the quantum critical point, we explore the crossover from quantum criticality: direct visualization of the development of a quantum phase transition, the parameter space for quantum criticality, as well as universality and scaling behaviors
Estienne, Benoit. "Étude des systèmes critiques bidimensionnels possédant des symetries discrètes : les th\éories conformes parafermioniques, et leurs applications." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00421566.
Benazzouz, Adrien. "Approches comparées des paramètres de Hansen et du modèle COSMO-RS pour l'étude des phénomènes de solubilisation : application à la caractérisation et à la valorisation des agro-solvants." Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10130.
The evolution of regulations and the global awareness as result of health and environmental issues are deeply modifying the solvent landscape. With the increasing demand for alternative solvents, such as biosolvents, there is a need for systematic physicochemical tools for the characterization of their solubilizing properties. The Hansen solubility parameters, derived from the theory of Hildebrand, provide a representation of the main molecular interactions in solution. Their applucation performance were tested in order to characterize emerfinf biosolvents and to study the solubilization of molecular and macromolecular solutes. In contrast, the COSMO-RS model combines quantum chemistry and statistical thermodynamics to predict molecular properties int the liquid state. The performance of this model was evaluated and used to account for the solubility phenomena of complex solutes such as nitrocellulose and fullerene-C60. With their ability to handle the two main mechanisms of solubilization (similarity and complementarity), the COSMO-RS descriptors were used to create new solubility parameters as simple as those of Hansen but more scientifically rigorous. This renewal of the solubility parameters is based on the consideration of the Lewis acide-base interactions and the new concept of COSMOmorphe for the calculation of dispersive interactions. These considerations enable the development of a green degreasing microemulsion whose efficiency is based on an unusual mechanism of degreasing-stripping
Richard, Jérémie. "Propagation d'atomes ultra-froids en milieu désordonné - Étude dans l'espace des impulsions de phénomènes de diffusion et de localisation." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLO001/document.
The work presented in this thesis is linked to the observation in momentum space of diffusion and localization phenomena using matter waves in optical disorder. We start by a general introduction on disorder physics and propagation in complex media by describing diffusion and localization phenomena such as the coherent backscattering or the Anderson localization. Then, we develop the experimental aspect of our work which is related to ultra-cold atoms, manipulated and controlled in order to create a coherent matter-wave analogous to a plane wave. Optics is an essential aspect of our work, that is why we present a complete experimental study of the system of creation of our disorder, called speckle field. These preliminary steps allow us to describe the research done by our team. An elementary parameter of diffusion, the elastic scattering time has been experimentally measured for an attractive and a repulsive speckle field. A weak localization phenomenon visible in momentum space, the coherent backscattering, observed for the first time with ultra-cold atoms, is then presented. The consequent study of the resurgence of coherent backscattering, done by our team, is based on the manipulation of an essential property for coherent propagation in disorder: the time reversal symmetry. Finally, we present a preliminary study of a novel signature in momentum space of the Anderson localization called coherent forward-scattering
Böhm, Julian. "Phénomènes de transport originaux dans des expériences micro-ondes via la mise en forme spatiale et spectrale." Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4048/document.
Transport of waves plays an important role in modern communication systems like Wi-Fi or optical fibres. Typical problems in such systems concern security against possible intruders, energy consumption, time efficiency and the possibility of mode filtering. Microwave experiments are suited to study this kind of problems, because they offer a good control of the experimental parameters. Thus we can implement the method of wave shaping to investigate atypical transport phenomena, which address the mentioned problems. Wave front shaping solely based on the transmission together with the Wigner-Smith time delay formalism allows me to establish special scattering states in situ. These scattering states avoid a pre-selected region, focus on a specific spot or follow trajectories of classical particles, so called particle-like scattering states. Mode filtering is induced inside a waveguide with wavy boundaries and position dependent loss. The boundary profiles are chosen in such a way that the two propagating modes describe an encircling of an exceptional point in the Bloch picture. The asymmetric mode filtering is found due to the appearing non-adiabatic transitions. Another part of my work deals with Grover’s quantum search. I put such a search into practice in a two-dimensional graphene-lattice using coupled resonators, which form a tight-binding analogue. In this proof of principle experiment we search for different resonators attached to the graphene-lattice. Furthermore, the scaling behaviour of the quantum search is quantified for a linear chain of resonators
Colin-Gouillou, Marie. "Etude théorique de l'échange isotopique H/D et 16-O/18-O sur la surface (001) de MgO." Poitiers, 1999. http://www.theses.fr/1999POIT2294.
Boudier, Dimitri. "Etude des phénomènes de transport de porteurs et du bruit basse fréquence en fonction de la température dans les transistors FinFET et GAA NWFET sub-10 nm." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC220/document.
The work led within this thesis focuses on the study of advanced MOSFET technologies, more precisely of triple-gate FinFETs and Gate-All-Around nanowire FETs. They were fabricated for the 10-nm technological node, following the same recipe except for the build of a fourth gate in nanowire devices.The devices have been studied in static regime in order to determine the main parameters of their electrical model. Low temperature (<10 K) and low drain voltage (1mV) studies highlighted the existence of quantum transport that is due to discrete energy levels within the conduction and valence bands. The study of the 1/f noise testifies the good control of the gate oxidation process and evidences a change in the noise mecanism under quantum transport.Numerous low frequency noise spectroscopies (i.e. study of the generation-recombination noise as a function of the temperature) let us identify silicon film traps, thus giving indication of the critical process steps that are responsible for the generation-recombination noise